(1) Field of the Invention
The present invention relates to systems, devices, methods, and programs for exclusively controlling resources, and in particular, to a system, a device, a method, and a program which require an exclusive control of resources.
(2) Description of the Related Art
In a communication control system, an exclusive control of resources is generally performed so as to prevent a single resource in the communication control system from being accessed by a plurality of terminals at the same time.
For example, in the case of mobile terminals communicating with a base station, there is a limit in the number of mobile terminals (communication resources) that can be connected with the base station at the same time. Thus, even if an urgent communication is required in the event of an emergency, such as a disaster, communication resources may be insufficient, not allowing the communication to the required emergency contact.
In order to address such problems, there is a proposed technique which allows continuation of communication to an emergency contact (See Patent Literature 1: Japanese Patent Application Publication No. 2007-251644). In the technique, when a mobile terminal makes a call, a present location and a destination of the mobile terminal are notified as a location information notifying signal so as to reserve communication resources of communication base stations existing on a traveling route from the present location to the destination.
Furthermore, in recent years, processors referred to as multi-task processors which can process a plurality of tasks in parallel (hereinafter, collectively referred to as “multi-processors”) have started to be used. Thus, techniques of exclusive control of resources in the multi-processors have also been studied.
For example, there is a proposed technique for exclusively controlling resources in a multi-processor (see Patent Literature 2: Japanese Patent Application Publication No. 2007-219800). The technique includes the following steps: an interrupt inhibit step for inhibiting the execution of a task from being interrupted in a unit processor on which the task is executing; an exclusive control step for performing an exclusive control between the unit processor and other unit processors by acquiring an inter-unit processor lock after the interrupt inhibit step causes a unit processor interrupt inhibit state; and an external interrupt inhibit step for inhibiting the performance of interrupt handling requested from the outside after the exclusive control step performs the exclusive control between the unit processor and the other unit processors.
However, the conventional technique disclosed by Patent Literature 1 is based on an assumption that a mobile terminal has already established communications with a base station. Therefore, for example, in the case where an emergency communication needs to be made by a mobile terminal that has not yet established communications with the base station, the communication to the emergency contact cannot be established, which is not effective.
The conventional technique disclosed by Patent Literature 2 requires a step for inhibiting an interrupt from the outside at the time of performing an exclusive control in a multi-processor, which results in a degraded response to the interruption. In particular, real-time capability is important for an embedded appliance having a multi-processor; and thus, the degraded interrupt response in the exclusive control of resources may lead to a major problem.
The present invention has been conceived in view of the above, and has an object to provide a system, a device, a method, and a program for exclusively controlling resources which allow a device which has not yet obtained a resource to secure the necessary resource without degrading response to resource obtainment.